Quick freezing of foods



Aug. 19, 1947.

J. M; BAER QUICK FREEZING 0F FOODS Filed ot. 12. 1%

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QUICK FREEZIN G OF FOODS John M. Baer, Chicago, Ill.,v assignor to The Guardlte Corporation, a `corporation of Illinois Application October 12, 1944, Serial No. 558,400l

3 Claims. (Cl. 99-192) and cake on the cold surfaces and interfere with cooling. The removal of such caked ice interferes with the continuity of the process.

On the other hand, some efforts have been made to freeze materials by evaporation of moisture therefrom. Such processes can be worked where the amount of material involved is very minute, but the enormous volumes of water required to be handled make such a process unworkabie on a large scale for bulkmaterials.

preferably continued during the cooling to remove any water which may be generated. Cooling is accomplished primarily by radiation of the heat of the product to cooling plates or walls adjacent the product. These walls are maintained at a temperaturemarkedly below the temperature of the product, for example, as low as 260 F.

The pre-evacuation and precooling after the blanching' step remove superficial water from the product to such a degree as to avoid caking of ice upon the plates during cooling, and caking may be further avoided by maintaining a pressure in the chamber below or substantially at the vapor pressure of water at the temperature of the cooling plates.

In the present process the food product is lafter removal of air and substitution of an atmosphere of steam at very low pressure, is subjected to steam at increasing temperature and pressure until it has reached a blanching temperature Whiclnis ordinarily over 165 F. The blanching temperature may, however, be considerably higher than this, as, for example, as high as 230 F. on some products suchas certain meats. The blanching operation continues at this temperatue for'a short time. Usually from 2 to 10 minutes is suflicient to accomplish blanching. Thereafter the product is cooled by evacuation of moisture until the product has reached a temperature only slightly above its freezing point. For most products a temperature of about 35 F. is satisfactory. In s ome instances where the freezing point is markedly les's than 32 F., a corresponding reduction in the minimum temperature should be accomplished.

The cool product, preferably without contact with air, is then subjected to radiant cooling. Radiant cooling is accomplished in an atmosphere preferably of high vacuum and in the ablsence, so far as possible, of gases that interfere with radiation, such as CO2. Evacuation is also The process is preferably progressive and continuous, the food being passed on a conveying system through a chamber adjacent to cooled walls. The Walls may of course be progressively cooler as the product proceeds through the chamber.

The invention is illustrated` diagrammatically in the drawings, in which I0 represents a blanching chamber having a steam inlet Il vacuum line I2 leading to any suitable evacuating'means. From the blanching chamber I0 the product is passed in any suitable way to the conveyor I3 in the radiant cooling-chamber I4.

lThis chamber likewise has a vacuum line l5.

Above the product is a series of cooling walls or plates 20 which are provided with a cooling medium in any suitable manner. The plates may be made progressively cooler if desired. Where the product is solid and maintained on a screen, the. cooling plates may also be positioned below the product as indicated at 2|. The product is removed from the chamber in any suitable way.

The invention may also be used for the treatment of non-food products Where it is desired to freeze the material, provided the material originally contains a substantial quantity of water.

'Ihe radiant lwalls 2l) and 2l of the chamber should be as dark in color as possible, and preferably black. For this purpose a lamp black coating may be desirable.

taining food product which comprises blanching and a outspreadform and out of contact with a refrig-4 erating surface, through a chamber having black walls cooled to a temperature of approximately ,-200" F. wherein the heat of the product is radiated in substantial quantities to the walls and the product is quick-frozen in the chamber, the enj tire method being conducted in the substantial 'absence of air and the freezing chamber being continuously evacuated at a pressure below the vapor pressure o f water at the temperature of the cooling Walls.

2. In a method of freezing a moisture-containing food product which comprises blanching the product at a temperature in excess of 165 F. by removing air therefrom and substituting an atmosphere of steam and evacuating the product to reduce its temperature to a. point just above the freezing point of water in the product, the step which comprises passing the material in outspread form and out of contact with a refrigerating surface through a highly evacuated chamber having black walls adjacent the product, said walls being cooled to a temperature of approximately minus 200 F. lwherein the heat of the material is radiated in substantial quantities to the walls and the product is quick-frozen in-the chamber, the entire method being conducted in the substantial absence of air.

3. In a method of freezing a moisture-containing food product which comprises blanching the product at a temperature substantially above atmospheric by removing air therefrom and substituting an atmosphere of steam and evacuating the product to reduce its temperature to a point just above the freezing point of water in the product, the step which comprises passing the material in outspread form and out of contact with a refrigerating surface through a cooling chamber having walls adjacent the product cooled to a markedly lower temperature than the product, wherein the heat of the material is radiated in substantial quantities to the walls and the product is quick-frozen in the chamber, the entire method being conducted in the substantial absence of air and said cooling chamber being continuously maintained during the freezing operation at a pressure below the vapor pressure of ywater at the temperature of the walls.

JOHN M. BAER.

REFERENCES CITED The following references are of record in th file of this patent: i

UNITED STATES PATENTS Number Name Date 1,884,429 Warner Oct. 25, 1932 1,955,484 Birdseye Apr. 17, 1934 2,109,002 Warren Feb. 22, 1938 2,116,813 Weisser et al May 10, 1938 2,345,204 Logwg Mar. 28, 1944 FOREIGN PATENTS Number Country Date 13,008' Great Britain 1895 489,939 Great Britain 1938 368,013 Great Britain 1932 

